Felony assault charges are pending against a 15-year-old boy accused of assaulting a staff member last week at a Mercer County juvenile detention facility, state police said.

The incident at about 10:10 p.m. Wednesday at George Junior Republic left the 24-year-old victim hospitalized with a serious head injury.

Police said the staff member was attempting to escort the boy in connection with another incident when the teen “began to actively resist,” causing both of them to fall to the ground.

“While falling to the ground,” according to a police report, “the victim struck his head on the corner of a chair and became unconscious.”

The boy allegedly struck the employee before being pulled away by another staff member.

The injured New Castle man was taken to Grove City Medical Center, and later flown by medical helicopter to Allegheny General Hospital in Pittsburgh. His condition was not available Sunday.

Police did not release the name of the boy, who is facing possible charges including aggravated assault.

George Junior Republic is a residential school for juvenile boys sent there by the courts or through private placement.

Officials at the facility could not be reached for comment Sunday.